U.S. Pat. No. 4,406,773 to Hettinger, Jr. et al. teaches hydrocarbon conversion in conjunction with a magnetic separator.
U.S. Pat. No. 5,147,527 to Hettinger teaches a combination of hydrocarbon conversion by contact with fluidized particles and the magnetic separation of such particles on a moving belt to reject highly metal contaminated particles.
U.S. Pat. No. 5,230,869 to Hettinger et al. teaches hydrocarbon conversion apparatus comprising magnetic separator means and means for adding a magnetically active moiety onto particles circulating in a hydrocarbon conversion system so that the moiety deposits on the circulating particles proportionate with the time the particles have been circulating in the hydrocarbon conversion system.
U.S. Pat. No. 5,171,424 to Hettinger teaches a hydrocarbon conversion process comprising addition of a paramagnetic active heavy rare earth-containing compound to catalyst circulating in the hydrocarbon conversion system, and separation of particles containing higher concentrations of paramagnetic heavy rare earth by magnetic separation means.
U.S. Pat. No. 5,393,412 to Hettinger teaches recovering and reconditioning metal-laden particulate catalyst or sorbent by passing it through a magnetic separator to separate out high metal low activity particulate and passing the metal laden particulate through a particle size classifier and/or passing a portion of the larger particles to attriting means wherein the larger particles are reduced in size and metal content.
Re. 35,046 (formerly U.S. Pat. No. 5,106,486) to Hettinger, Jr. et al. teaches hydrocarbon conversion comprising intentionally adding continuously or periodically a magnetically active moiety so it deposits on the particles over a period of time and separating out older particles added earlier to the system from newer particles later added, by magnetic means.
U.S. Pat. No. 5,190,635 to Hettinger teaches operating a hydrocarbon conversion process for contacting hydrocarbons containing various amounts of iron, nickel and/or vanadium with particles wherein metals are deposited on the particles, operating the conversion process so as to accumulate on said particles at least 4500 ppm iron compounds and so as to render at least a portion of said iron compounds supermagnetic or ferromagnetic, and magnetically separating more highly magnetic particles from less magnetic particles and recycling at least a portion of the less magnetic particles.
The above prior art teaches the advantages and techniques useful for the magnetic separation of hydrocarbon conversion catalysts which have been contaminated by metals and thereby reduced in conversion activities. Previously, the separation could be varied only by changing the speed (drum rotation or disc rotation in drum and disc magnetic separators) and the thickness of the belt, drum or disc as well as the magnetic field to which the catalyst particles are subjected and also by varying the splitter setting so that the cut (percent rejected) is varied as the catalyst moves off the element which conveys the catalyst through the magnetic field in the magnetic separation device. The present invention adds a new variable for the more close control of the separating out of the metal contaminated catalyst and extends the applicability of magnetic separation even to catalyst particles which are so metal contaminated that they previously posed problems in magnetic separations due to their extremely high magnetic susceptibilities.